The eye examination is widely known as an effective method capable of diagnosing at early timing the type of a disease that may lead to a lifestyle related disease or blindness. An optical coherence tomography (OCT) or a comparable tomography imaging apparatus enables an eye doctor or any other specialist to observe a three-dimensional state of internal retinal layers.
For example, the retina has a layer structure that is composed of a plurality of layers. Information relating to thickness of each layer etc. is usable as an objective index that indicates the stage of a disease.
In order to observe the retinal layer structure or to obtain the index, a technique capable of analyzing a tomography image of retinal layers is used to identify the layer structure.
A conventional method discussed in Japanese Patent Application Laid-Open No. 2008-73099 includes performing preprocessing (e.g., gradation conversion) on a tomography image and detecting an edge from the processed image in the depth direction. The above-described conventional method further includes identifying the position of a layer boundary based on the position of a detected edge.
The layer structure of retinal layers includes a locally deformed region where a characteristic part (e.g., optic disc or macula) is present. Further, if the layer structure includes a blood vessel or a leucoma, signal light may not reach an underlying region beneath the above-described portions and a target layer boundary to be identified may not be included in a captured image.
However, the conventional processing discussed in Japanese Patent Application Laid-Open No. 2008-73099 does not take the above-described local change in the layer structure into consideration. Therefore, the layer structure identification with the method may be failed.